Stainless steel tubes with optical waveguides are widely used, for instance in submarine cables, in the metal screen of power cables and in overhead power lines (WO 96/31885, EP 0 285 917, EP 0 286 804).
A method for manufacturing an optical cable unit, comprising a metal tube and several optical waveguides therein is disclosed in U.S. Pat. No. 5,768,762.
A metal tape of austenitic steel is gradually shaped into a lengthwise slotted tube, the optical waveguides are introduced into the still open slotted tube, the lengthwise slotted tube is welded and the outside diameter of the welded tube is reduced.
From EP 1 184 128 it is known to produce metal tubes of copper by welding the seam with a laser beam. Copper reflects the laser beam and it is therefor difficult, to input the laser energy into the copper material.